Panoramic radiographic apparatus and digital sensor cassette used for same apparatus

ABSTRACT

The panoramic radiographic apparatus of the present invention has a cassette holder capable of accommodating both a conventional film cassette and a digital sensor cassette loaded with an electric X-ray image detector, one at a time, in a rotary arm, wherein when a film cassette is mounted, the cassette holder is mechanically moved in accordance with the rotation of the rotary arm so as to carry out panoramic radiographing, and when a digital sensor cassette is mounted, without moving the cassette holder, the electric X-ray image detector is driven by supplying control signals corresponding to the rotation of the rotary arm to the digital sensor cassette to obtain image signals required for generating a panoramic X-ray image. Therefore, both the film cassette and the digital sensor cassette can easily be mounted, one at a time, whereby required panoramic X-ray images can be obtained by fully using the features of each type of cassette.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a panoramic radiographic apparatus forentire jaw photographing and the like in dental examination andtreatment for example, and to a digital sensor cassette used for thesame apparatus.

2. Description of the Prior Art

A panoramic radiographic apparatus used in dental, otorhinolaryngologicand other clinics has a support for rotatably supporting a rotary armprovided with an X-ray generator at one end thereof and an X-raydetector at the other end thereof, and a film cassette loaded with anX-ray film is mounted in the X-ray detector and moved at a predeterminedspeed in accordance with the rotation of the rotary arm so as to carryout panoramic radiographing. In addition, it is also known that insteadof the film cassette, a digital sensor cassette loaded with an electricX-ray image detector is mounted in the X-ray detector, and the electricX-ray image detector is driven under the control of control signalscorresponding to the rotation of the rotary arm so as to obtain imagesignals required for generating a panoramic X-ray image (for example, inJapanese Laid-open Patent Application No. Hei 9-135829 and U.S. Pat. No.5579361).

The apparatus disclosed in Japanese Laid-open Patent Application No. Hei9-135829 is provided with both a film cassette and a digital sensorcassette so that either cassette can be selectively used depending onthe object of operation, whereby the trouble of replacement iseliminated, and examination and treatment can be made speedily. However,the structure of the X-ray detector becomes complicated, an X-raydetector for generally-used film cassettes cannot be used, that is, aspecial X-ray detector is necessary. Furthermore, the digital sensorcassette is built in the apparatus and does not have a structure to beinserted into and withdrawn from a cassette holder. Moreover, theconfiguration of the digital sensor cassette as a single cassette hasnot been disclosed specifically.

In the apparatus disclosed in the USP, a digital sensor cassette ismounted in a cassette holder, and this cassette holder is moved. Inaddition, a structure for detecting the speed of the movement isnecessary, making the structure of the X-ray detector complicated.Furthermore, there is no concrete disclosure indicating any structurefor replacing the film cassette with the digital sensor cassette,whereby the replacement is made with difficulty.

Furthermore, a panoramic radiographic apparatus using a digital sensoris superior to a panoramic radiographic apparatus using a film in thatbecause no development is necessary, a panoramic X-ray image can beobtained immediately and can be widely used for examination andtreatment through the use of computers. However, almost all thepanoramic radiographic apparatuses used in clinics are types used withfilm cassettes, and cannot be used with digital sensor cassettes. Forthese reasons, if the panoramic radiographic apparatuses used with filmcassettes can be used with digital sensor cassettes by slightmodifications, a great advantage can be expected.

SUMMARY OF THE INVENTION

In accordance with the above, an object of the present invention is toprovide a panoramic radiographic apparatus wherein both a film cassetteand a digital sensor cassette can easily be mounted in and removed fromthe X-ray detector of the apparatus, one at a time, without making thestructure of the X-ray detector complicated. Another object of thepresent invention is to provide a digital sensor cassette compatiblewith the film cassette.

In order to attain the above-mentioned objects, the panoramicradiographic apparatus of the present invention is an apparatus having asupport for rotatably supporting a rotary arm provided with an X-raygenerator at one end thereof and an X-ray detector at the other endthereof, comprising a cassette holder capable of accommodating both afilm cassette loaded with an X-ray film and a digital sensor cassetteloaded with an electric X-ray image detector, one at a time, at theX-ray detector, and a control means for performing electric control sothat when a film cassette is mounted in the cassette holder, thecassette holder accommodating the film cassette is mechanically moved inaccordance with the rotation of the rotary arm at a predetermined speedin a direction nearly perpendicular to X-ray beams applied from theX-ray generator to the X-ray detector so as to carry out panoramicradiographing using a film, and so that when a digital sensor cassetteis mounted in the cassette holder, with the cassette holderaccommodating the digital sensor cassette being in a secured conditionwith respect to the X-ray detector, the electric X-ray image detector isdriven by supplying control signals corresponding to the rotation of therotary arm from the main body of the panoramic radiographic apparatus tothe digital sensor cassette to obtain image signals required forgenerating a panoramic X-ray image.

The digital sensor cassette for the panoramic radiographic apparatus ofthe present invention comprises at least an electric X-ray imagedetector disposed in face-to-face relationship with the X-ray generatorvia an X-ray shield plate having a secondary slit and provided at theX-ray detector, driven by control signals supplied from the main body ofthe panoramic radiographic apparatus in correspondence with the rotationof the rotary arm, and used to convert X-rays to electric signals todeliver image signals required for generating a panoramic X-ray image;an A/D converter for converting analog signals delivered from theelectric X-ray image detector into digital signals; an input/outputportion for communicating with an external circuit; and a controlportion for electrically controlling the operations of theabove-mentioned various portions. The outer housing of the digitalsensor cassette is nearly identical with a conventional film cassetteloaded with an X-ray film in shape, and the digital sensor cassette canbe mounted in the cassette holder for the film cassette, provided at theX-ray detector of the panoramic radiographic apparatus.

With these configurations, both the film cassette and the digital sensorcassette can easily be mounted in the cassette holder of the panoramicradiographic apparatus, one at a time, whereby required panoramic X-rayimages can be obtained by fully using the features of each type ofcassette.

The concrete configurations of the panoramic radiographic apparatus andthe digital sensor cassette of the present invention will be clarifiedby the following descriptions regarding embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective overall view showing a panoramic radiographicapparatus in accordance with an embodiment of the present invention;

FIG. 2 is a sectional view showing the X-ray detector of the apparatus;

FIG. 3 is a perspective view showing an example of a film cassette forthe apparatus;

FIG. 4 is a perspective view showing an example of a digital sensorcassette used for the apparatus;

FIG. 5 is a perspective view showing the structure of the electric X-rayimage detector of the digital sensor cassette;

FIG. 6A is a perspective view showing the main portion of the filmcassette;

FIG. 6B is a side view showing the main portion of the film cassette;

FIG. 7A is a perspective view showing the main portion of the digitalsensor cassette;

FIG. 7B is a plan view showing the main portion of the digital sensorcassette;

FIG. 8A is a plan view illustrating a method of mounting the digitalsensor cassette;

FIG. 8B is a plan view illustrating the method of mounting the digitalsensor cassette;

FIG. 9 is a partially cutaway plan view showing another securing meansfor the digital sensor cassette;

FIG. 10 is a partially cutaway plan view showing still another securingmeans for the digital sensor cassette;

FIG. 11 is a flowchart showing a procedure of position control by thesecuring means shown in FIG. 10;

FIG. 12 is a block diagram of the control circuit of the apparatus;

FIG. 13 is a block diagram of a control circuit of the digital sensorcassette;

FIG. 14 is a block diagram of another control circuit of the digitalsensor cassette;

FIG. 15 is a block diagram of still another control circuit of thedigital sensor cassette;

FIG. 16 is a block diagram of yet still another control circuit of thedigital sensor cassette;

FIG. 17 is a view showing a method of mounting the digital sensorcassette in a charger for the digital sensor cassette; and

FIG. 18 is a block diagram showing control circuits of the charger andthe digital sensor cassette.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, embodiments of the present invention will be described below.

Referring to FIG. 1, the numeral 1 designates the main body of apanoramic radiographic apparatus. A column 3 stands on a base 2, and asupport 4 is mounted on the column 3 so as to be movable vertically. Arotary arm 5 is rotatably mounted on the support 4. A support arm 4 aand a patient frame 4 b, both extending in the horizontal direction, areprovided at the upper and lower ends of the support 4, respectively. Thepatient frame 4 b is provided with a chin rest 4 c. The support arm 4 aaccommodates an XY table capable of being moved freely in the X and Ydirections by stepping motors. The rotary arm 5 is suspended via this XYtable so as to be movable as desired in a horizontal plane. The numeral4 d designates a patient's head holder disposed passing through therotary arm 5 on the lower surface of the support arm 4 a. The headholder 4 d is equipped with a position adjustment mechanism.

The rotary arm 5 is provided with a rotary mechanism for rotating therotary arm 5 around the support arm 4 a by using a stepping motor. Therotary arm 5 is configured so as to rotate around its vertical axiswhile its rotation center is moved by the XY table. The rotary arm 5 hashanging portions at both ends thereof. An X-ray generator 6 is providedat one end 5 a of the rotary arm 5, and an X-ray detector 7 is providedat the other end 5 b in face-to-face relationship with each other. TheX-ray generator 6 is equipped with an X-ray tube, an X-ray shield platehaving a vertical primary slit, an adjustment mechanism for changing theshape of the primary slit and the like.

A shield plate 8 having a vertical secondary slit 8 a corresponding tothe primary slit and an adjustment mechanism for the secondary slit 8 ais provided at the X-ray detector 7 in face-to-face relationship withthe X-ray generator 6. Behind the shield plate 8, a cassette holder 9 isdisposed. As shown in FIG. 2, the cassette holder 9 is supported by aslide bearing 9 a so as to be movable in the horizontal directionperpendicular to the surface of the drawing in FIG. 2. The cassetteholder 9 is provided with a drive motor 9 b.

A control portion 11 comprising a PC board having a variety of circuits,and an operation panel 12 for covering the outside the control portion11 are provided behind the slide bearing 9 a of the X-ray detector 7.Various switches and a liquid crystal display portion (not shown) aremounted on the operation panel 12. In addition, a remote-control box 13is provided, which is connected to the main body 1 of the apparatus viaan operation cord 13 a. The remote-control box 13 is provided with amain switch for power on/off operation and an X-ray irradiation switch,for example.

When entire-Jaw panoramic radiographing is carried cut by using a film,the head of a patient is secured to a predetermined position on thepatient frame 4 b, and a film cassette 21 loaded with an X-ray film ismounted in the cassette holder 9 as shown in chain lines in FIG. 2.X-rays are then applied from the X-ray generator 6 to the X-ray detector7. While the rotary arm 5 is rotated, the center of the rotation ismoved along a predetermined track. In synchronization with thismovement, the cassette holder 9 accommodating the film cassette 21 ismoved together with the cassette 21 in the horizontal direction at apredetermined speed. This movement is carried out by the drive motor 9b. The direction of the movement with respect to the X-ray detector 7 isalmost perpendicular to the X-rays applied from the X-ray generator 6.FIG. 3 shows an example of the film cassette 21 replaceably loaded withan X-ray film and a sensitizing paper sheet. A conventional filmcassette having been used generally is used here without modification asthe film cassette 21.

Since the above-,mentioned operations, and the basic configuration andoperations of the main body 1 of the apparatus wherein a film cassetteis used have been known, further explanation is omitted. However, asdescribed later, in the apparatus in accordance with the presentembodiment, a variety of circuits required when a digital sensorcassette is used are provided in the control portion 11. Furthermore,the X-ray detector 7 is provided with a connector 14 for connection tothe digital sensor cassette.

FIG. 4 shows an example of a digital sensor cassette 22 used for theapparatus. When a conventional film cassette having been used generallyis used without modification as the film cassette 21 as described above,a cassette holder for the conventional film cassette can also be usedwithout modification as the cassette holder 9. As shown in FIG. 2, theupper and lower edges of the cassette holder 22 are each equipped with acassette support piece 9 c having a shape of L in cross section.Therefore, the dimensions and shape of the outer housing 23 of thedigital sensor cassette 22 are made nearly identical with those of thefilm cassette 21. In particular, the dimensions and shapes of the upperedge 23 a and the lower edge 23 b of the outer housing 23 areselectively determined to have dimensions and shapes so as to beinsertable and mountable in the space between the cassette supportpieces 9 c, 9 c of the cassette holder 9.

The cassette holder 9 of the X-ray detector 7 should only be configuredso that the film cassette 21 and the digital sensor cassette 22 can bemounted smoothly therein, one at a time. For example, without using theconventional film cassette having been used generally as the filmcassette 21, by using the cassettes 21 and 22 specially made for thisapparatus, the cassette holder 9 configured to be adapted for thespecial cassettes can also be adopted.

The digital sensor cassette 22 is equipped with an electric X-ray imagedetector and various circuits related thereto inside the outer housing23. A connector 24 for connection to an external circuit is provided onone side of the housing 23. This connector 24 is usually connected tothe connector 14 of the X-ray detector 7 by a cable integrallycontaining power lines and signal lines. In addition, the connector 24can also be connected to an external device such as a personal computer.The outer housing 23 is formed of an appropriate material havingnecessary strength, for example metal, such as an aluminum sheet, orsynthetic resin, such as ABS resin. At the front center of the outerhousing 23, an X-ray receiver 25 formed of a material having hightransmittance for X-rays and capable of shielding visible light, such asdark-colored ABS resin or the like, is provided in the verticaldirection in correspondence with the secondary slit 8 a. Inside theX-ray receiver 25, the electric X-ray image detector is disposed.

FIG. 5 is a view showing the general structure of the electric X-rayimage detector and a protection case for the detector. The electricX-ray image detector 26 has a three-layer structure comprising a lightemitter for emitting light when irradiated with X-rays, i.e., ascintillator 26 a, an optical fiber device 26 b for transmitting thelight emitted from the light emitter 26 a, and an image pickup deviceportion 26 c formed of a semiconductor sensor, such as CCD or MOS,having two-dimensionally disposed pixels of an image pickup device. Thisthree-layer structure is integrally provided on a ceramic base 26 d. Thenumeral 27 designates the protection case, and the numeral 27 adesignates a shield material.

In FIG. 5, the thicknesses of the components of the electric X-ray imagedetector 26 are exaggerated. The actual thicknesses of the componentsare as follows: the light emitter 26 a is 0.3 mm, the optical fiberdevice 26 b is 1.5 mm, the image pickup device portion 26 c is 0.5 mm,and the ceramic base 26 d is 1 mm in thickness, for example.Furthermore, the pixel configuration of the image pickup device portion26 c is a two-dimensional arrangement of square pixels measuring 96 μmon each side and disposed so as to form a rectangle measuring about 6 mmin width and about 150 mm in length. The signals of the image pickupdevice portion 26 c are taken out of electrodes 26 e disposed on theback side of the ceramic base 26 d.

The protection case 27 is formed of a lightproof material to eliminatethe influence of visible light on the electric X-ray image detector 26.The electric X-ray Image detector 26 is covered with this protectioncover 27, and is also covered with the X-ray receiver 25 on the frontside thereof. In this covered condition, the electric X-ray imagedetector 26 is housed in the housing 23. In the case that the housing 23is lightproof, it is possible to omit the protection case 27.

Because of the above-mentioned configuration, a panoramic X-ray imagecan be obtained in the form of digital signals by the electric X-rayimage detector 26. Since the image pickup device portion 26 c comprisesa semiconductor sensor, such as CCD, the digital sensor cassette 22 canhave high sensitivity. In addition, while protected against visiblelight, the electric X-ray image detector 26 can smoothly receive X-rays,thereby making it possible to carry out clear radiographing.

Next, means for positioning and securing the digital sensor cassettewill be described below. FIGS. 6A to 9 show examples of mechanicalmeans, and FIGS. 10 and 11 show examples of electrical means.

The cassette holder 9 is supported on the side of the end 5 b of therotary arm 5. Referring to FIGS. 6A and 6B, the numeral 9 a-1 designatesa sliding member on the arm side, secured to the end 5 b, and thenumeral 9 a-2 designates a sliding member on the cassette holder side,secured to the back side of the cassette holder 9. A rod-like tighteningmember 10 a having a male thread 10 b at its end is secured with a clamp10 c to the sliding member 9 a-1 on the arm side in the longitudinaldirection thereof. In addition, as shown in FIGS. 7A and 7B, a mountingplate 10 d is secured to one side of the digital sensor cassette 22 byscrews, a positioning plate 10 e is secured to the mounting plate 10 d,and a tightening member 10 f having a female thread log at its end isrotatably mounted on the mounting plate 10 d.

A method of mounting the digital sensor cassette 22 in the X-raydetector 7 is described below. First, the cassette 22 is mounted in thecassette holder 9 as shown in FIGS. 6B and 8A. The end of thepositioning plate 10 e is made contact with the end surface of thesliding member 9 a-2 on the cassette holder side. Since the length ofthe cassette holder 9 is the same as that of the digital sensor cassette22, the center of the cassette holder 9 indicated by line A is alignedwith the center of the digital sensor cassette 22 provided with theX-ray receiver 25 in this condition. Next, the cassette holder 9 and thedigital sensor cassette 22 are moved and inserted in the directionindicated by the arrow on the back side of the shield plate 8 so thatthe positioning plate 10 e makes contact with the end surface of thesliding member 9 a-1 as shown in FIG. 8B. The dimensions of the membershave been selectively determined so that the X-ray receiver 25 at thecenter of the digital sensor cassette 22 is aligned with the center ofthe secondary slit 8 a of the shield plate 8 indicated by line B, and sothat the female thread 10 g of the tightening member 10 f is positionedso as to be engaged with the male thread 10 b of the tightening member10 a in this contact condition. By engaging the male thread 10 b withthe female thread 10 g and by tightening the tightening member 10 f, thedigital sensor cassette 22 can be secured to a predetermined position.

Instead of the above-mentioned thread engagement between the tighteningmember 10 f and the tightening member 10 a, a ball-plunger arrangementshown in FIG. 9 can also be used. In other words, instead of thetightening member 10 f, a tightening member 10 h having an engagementrecess 10 j is secured to the mounting plate 10 d. Furthermore, thetightening member 10 h is provided with an engagement portion 10 pwherein balls 10 k projecting into the engagement recess 10 j are pushedby screws 10 m and springs 10 n. The end of the tightening member 10 ais provided with an engagement member 10 r having an engagement groove10 q corresponding to the engagement portion 10 p. Because of thisconfiguration, when the digital sensor cassette 22 is inserted to thepredetermined position on the back side of the shield plate 8, theengagement member 10 r is inserted into the engagement recess 10 j, andthe balls 10 k of the engagement portion 10 p engage the engagementgroove 10 q, whereby the digital sensor cassette 22 is positioned andsecured at the same time. This securing can be released by pulling outthe tightening member 10 h by applying a force greater than theengagement force exerted between the engagement groove 10 q and theballs 10 k in correspondence with the pushing pressure of the springs 10n.

In an example using an electrical means shown in FIG. 10, a small slot10 s is provided at the end of the cassette holder 9. A reflectionmember 10 t is provided at a position corresponding to the slot 10 s onthe back side of the digital sensor cassette 22, that is, at a positionfacing the slot 10 s when the digital sensor cassette 22 is mounted inthe cassette holder 9 so that the center of the digital sensor cassette22 is aligned with the center of the cassette holder 9. The reflectionmember 10 t is formed of a reflective sheet attached to the digitalsensor cassette 22, for example. Furthermore, the end 5 b of the rotaryarm 5 is provided with a detection sensor 10 u equipped with alight-emitting device and a photodetector device. The position of thedetection sensor 10 u is determined so as to face the reflection memberlot when the cassette holder 9 and the digital sensor cassette 22 aremounted at the predetermined position.

The cassette holder drive motor 9 b is a stepping motor. After thedigital sensor cassette 22 is mounted in the cassette holder 9 and movednearly close to the predetermined position by hand, position control iscarried out in accordance with such a procedure as that shown in FIG.11, for example. More specifically, the output of the detection sensor10 u is read, and the drive motor 9 b is moved one step to the right orleft in accordance with the presence or absence of reflection, and theoutput of the detection sensor 10 u is read again. This operation isrepeated, and the motor is stopped and locked at a position wherein theresult of the detection of the presence or absence of reflection isreversed. In other words, in accordance with this procedure, when theboundary of the side edge of the reflection member 10 t has just reachedthe position facing the detection sensor 10 u, a judgment is made thatthe digital sensor cassette 22 has been mounted at the predeterminedposition. Therefore, the positions of the reflection member 10 t and thedetection sensor 10 u are determined to satisfy this condition.

As shown in FIG. 12, the control portion 11 comprises a control unit 11a, such as MPU or CPU, used as a central operation control unit for theentire apparatus, input/output ports 11 b and a memory 11 c. Inaddition, an X-ray irradiation control circuit 11 d, an X-rayirradiation detection circuit 11 e, an X-ray generation circuit 11 f, aprimary slit width adjustment circuit 11 g, a secondary slit widthadjustment circuit 11 h, a cassette position detection circuit 11 j, acassette drive circuit 11 k, a rotary arm rotation detection circuit 11m, a TDI clock generation circuit 11 n and the like are provided, andthese circuits are connected to the control unit 11 a via theinput/output ports 11 b.

The above-mentioned circuits have also been provided basically in aconventional apparatus used with film cassettes. The apparatus inaccordance with the present invention, however, further comprises acommunication control circuit 11 p, a cassette type detection circuit 11q, a photographing mode setting circuit 11 r, a power supply circuit 11s and the like. These circuits, the various switches and the displayportion on the operation panel 12, the various switches on theremote-control box 13 and the connector 14 are connected as shown inFIG. 12.

Furthermore, as shown in FIG. 13, the digital sensor cassette 22 isprovided with a control unit 22 a, such as MPU or CPU, for controllingthe operations of all the circuits in the cassette 22 and the operationsof the entire apparatus including the main body 1 of the apparatus,independently or integrated with the control portion 11 of the main body1 of the apparatus. The digital sensor cassette 22 is further providedwith input/output ports 22 b, a TDI clock conversion circuit 22 c, animage pickup device drive circuit 22 d, an A/D converter 22 e, a memory22 f, a communication control circuit 22 g, a power supply circuit 22 hand the like. These circuits, the electric X-ray image detector 26 andthe connector 24 are connected as shown in FIG. 13.

Next, panoramic radiographing by using the digital sensor cassette 22will be described below referring to FIGS. 12 and 13. First, the digitalsensor cassette 22 is mounted in the cassette holder 9. The cassette 22is secured to the predetermined position by the above-mentioned means byoperating the cassette position detection circuit 11 j and the cassettedrive circuit 11 k. The connector 14 is connected to the connector 24 byusing a cable 15 comprising wires or optical fibers and having aconnector 14′ on one end of the cable and a connector 24′ on the otherend, the connectors 14′ and 24′ being adapted to be connectable to theconnectors 14 and 24, respectively. By the connections, a predeterminedsignal circuit is formed, and communication is made possible between thedigital sensor cassette 22 and the main body 1 of the panoramicradiographic apparatus, whereby various signals are transmittedtherebetween. When the mounting of the digital sensor cassette 22 isdetected by the cassette type detection circuit 11 q, the radiographingmode for the digital sensor cassette 22 is selected, and variousconditions in accordance with this mode are set by the photographingmode setting circuit 11 r, whereby preparations for photographing arecarried out.

In this way, the type of a mounted cassette is detected by the cassettetype detection circuit 11 q, a photographing mode in accordance with thetype of the cassette is automatically selected, and predeterminedphotographing conditions are set. This eliminates the need for theoperator to select a photographing mode and to set photographingconditions in accordance with the type of the cassette to be used,thereby making the operation of the apparatus easy.

By making an arrangement so that the photographing mode for a filmcassette is selected when the mounting of a digital sensor cassette isnot detected, the automatic selection of the photographing mode is madepossible even when a film cassette having no communication function isused.

Photographing is started by turning on the X-ray irradiation switch onthe remote-control box 13. X-rays are applied from the X-ray generator 6to the X-ray detector 7. At the same time, the rotation center of therotary arm 5 is moved and the rotary arm 5 is rotated. At this time, thedrive motor 9 b of the cassette holder 9 is stationary, and a TDI clocksignal delivered at the time of photographing by using an ordinary filmcassette and synchronized with the rotation of the rotary arm 5, thatis, a signal for time delay integration control, is transmitted to thedigital sensor cassette 22 by the rotary arm rotation detection circuit11 m and the control unit 11 a. In accordance with this transmission ofthe signal, the image pickup device portion 26 c is driven. The TDIclock signal is supplied in a digital or analog form, and the cassette22 is configured to receive both types of signals.

When the image pickup device portion 26 c is driven, linear X-ray imageinformation required for generating a panoramic X-ray image is deliveredsequentially from the electric X-ray image detector 26, and transferredto the memory 22 f via the A/D converter 22 e. Generating a panoramicX-ray image is carried out sequentially beginning with its end, and theimage is stored. These operations are carried out during a periodbetween the transmission/reception of an X-ray irradiation start signaland the transmission/reception of an X-ray irradiation stop signal. Theimage process conducted at this time is an electrical process replacedwith the process in accordance with the principle of obtaining panoramicX-ray images by using a method wherein a linear X-ray image is subjectedto photosensing sequentially while a film cassette is moved insynchronization with the rotation of the rotary arm.

As clearly disclosed by the above descriptions, both the film cassetteand the digital sensor cassette can be used with the apparatus shown inthe figures, one at a time, whereby desired panoramic X-ray images canbe obtained by fully using the features of each type of cassette. Inparticular, the digital sensor cassette does not require development,whereby a panoramic X-ray image can be obtained immediately, therebybeing applicable to diagnosis using computers. Furthermore, by slightlymodifying an existing widespread panoramic radiographic apparatus usedwith a film, it is possible to obtain an apparatus which can be usedwith the digital sensor cassette in accordance with the presentinvention as well as the film.

The amount of X-ray dose in the case of the photographing mode for thedigital sensor cassette can be less than that in the case of thephotographing mode for the film cassette, because the sensitivity of theelectric X-ray image detector 26 is higher than that of the film. Owingto this reduction in the amount of X-ray dose, the amount of X-rayexposure to the subject to be photographed can be reduced. In this caseof using the digital sensor cassette 22, when the mounting of thedigital sensor cassette 22 is detected, the X-ray irradiation controlcircuit 11 d is automatically controlled on the side of the main body ofthe panoramic radiographic apparatus depending on the type of thesemiconductor sensor, such as CCD for example, used for the image pickupdevice 26 c and the voltage and current of the X-ray tube are set toappropriate values. However, it is possible to set the values bydesignating appropriate values on the side of the digital sensorcassette 22.

The communication between the digital sensor cassette 22 and the mainbody 1 of the panoramic radiographic apparatus is carried out under thecontrol of the communication control circuit 11 p. In mutualcommunication other than described above, information about thecassette, such as the serial number, photographing preparationconditions and operation conditions of the cassette, are transmittedfrom the cassette, and some operations of the main body 1 of theapparatus are controlled in accordance with the information about theoperation conditions. Even when operations which cannot be conductedsimultaneously are attempted by using commands during data processing ortransfer on the side of the main body 1 of the apparatus, such commandsare not accepted. As a result, malfunctions are prevented, and thereliability of operation is raised.

Furthermore, in addition to the above-mentioned TDI clock signal,various pieces of information about photographing, such as aphotographing mode, photographing preparation conditions, X-rayirradiation start/stop, X-ray tube voltage and current and an area to bephotographed are included in the information transmitted from thecontrol portion 11. These pieces of information can be used to obtainappropriate panoramic X-ray images, or used for diagnosis afterphotographing. The primary and secondary slits are adjusted in the caseof narrow slit photographing, and the conditions of the adjustments aretransmitted. In the case of 4-split photographing, information about thearea to be photographed and the like is also transmitted.

X-ray image information delivered from the electric X-ray image detector26 may be stored in the memory 11 c of the control portion 11 of themain body of the apparatus, instead of the memory 22 f of the digitalsensor cassette 22. Furthermore, as shown in FIG. 13, via the controlportion 11 of the main body 1 of the panoramic radiographic apparatusconnected to the connector 24, the apparatus can be connected to anexternal device 30, such as a personal computer or a large computer, ora network of these devices, and in this connection condition, apanoramic X-ray image can be indicated in real time on the display ofthe external device. It is also possible to connect the external device30 to the connector 24 after photographing to directly transfer an imageto the external device 30.

By using a device having a high processing capability as the externaldevice 30, it is possible to display not only panoramic X-ray images,but also data concerning photographing, such as a photographing mode,tube voltage, tube current and an area to be photographed. Moreover, itis possible to register these together with data concerning eachpatient, such as a patient name and ID number so as to use them fordiagnosis after photographing. In this way, a variety of uses are madepossible.

Electric power can be supplied to the digital sensor cassette 22 via theconnector 24, or via a power connection portion provided separately.However, since the digital sensor cassette 22 is an active deviceequipped with the memory 22 f and the control unit 22 a, the applicationrange of the cassette 22 can be expanded by using a dry cell or asecondary battery built inside or connected externally as a powersupply. FIG. 14 is a view showing an example wherein a secondary battery31 is mounted additionally in the configuration shown in FIG. 13.Instead of mounting the secondary battery 31 in the housing 23, anexternal battery 32 may be connected to a battery connection portion 32a disposed at an appropriate position in the housing 23 via requiredlead wires, or directly connected to the battery connection portion 32 aby using a removable connector capable of mechanical clamping. With sucha configuration, it is not necessary to provide a power supply circuiton the main body side of the panoramic radiographic apparatus, and nopower cable is required. Therefore, the panoramic radiographic apparatusused with film cassettes can easily be modified to an apparatus capableof using digital sensor cassettes.

Furthermore, when the secondary battery 31 is mounted as described abovein particular, no power cable is required to be connected. Besides,instead of using wire communication requiring cables, by using wirelesscommunication, no cable is required for communication. Since both cablesfor power and communication are not required, connection work can besaved, thereby enhancing rationalization. In this case, a non-contactwireless communication means, such as a means using infrared rays orradio waves, should only be added to the configurations shown in FIGS.12 and 13, and the connector 24 can be omitted. Even when the secondarybattery 31 is not mounted in the digital sensor cassette 22, it isneedless to say that a wireless type can be used as a communicationmeans.

FIG. 15 shows an example of an infrared communication means. The controlportion 11 of the main body of the panoramic radiographic apparatus isprovided with an infrared control circuit 33 a and itstransmission/reception portion 33 b. The digital sensor cassette 22 isprovided with an infrared control circuit 34 a and itstransmission/reception portion 34 b. As the transmission/receptionportions 33 b and 34 b, a light-emitting diode and a photo transistorare used. The light-emitting diode and the photo transistor are disposedso as to face each other when the digital sensor cassette 22 is mountedin the cassette holder 9. In particular, when the light-emitting diodeand the photo transistor are disposed to face very close to each other,the output can be made smaller, and the performance can be less affectedby interference.

FIG. 16 shows an example of a radio wave communication means. Thecontrol portion 11 of the main body of the apparatus is provided with aradio wave control circuit 35 a and its transmission/reception portion35 b. The digital sensor cassette 22 is provided with a radio wavecontrol circuit 36 a and its transmission/reception portion 36 b. Thefrequency of a radio wave and the type of modulation may be thoseadopted appropriately. Therefore, the locations of thetransmission/reception portions 35 b and 36 b can be selectivelydetermined more freely than those in the case of the infrared type.

When the secondary battery 31 is mounted in the digital sensor cassette22 as a power supply as shown in FIG. 14, the battery must be replacedor charged. FIGS. 17 and 18 show an example of a charger 41 used tocharge the secondary battery 31 while the battery is kept mounted in thedigital sensor cassette 22. A mounting portion 41 b for accommodatingthe digital sensor cassette 22 is formed in a housing 41 a, and theoutput portion 41 d of a built-in charging circuit 41 c is provided inthe mounting portion 41 b. In correspondence with this mounting portion41 b, the charge input portion 31 a of the secondary battery 31 isprovided on one end of the cassette 22. By inserting the end in themounting portion 41 b as indicated by the arrow shown in FIG. 17, theoutput portion 41d can be connected to the charge input portion 31 a soas to charge the secondary battery 31. The numeral 41 e designates apower cord connected to commercial electric power.

Furthermore, the charger 41 is provided with a communication circuit incorrespondence with the communication type of the digital sensorcassette 22. For example, in the case that the cassette 22 is providedwith the infrared transmission/reception portion 34 b shown in FIG. 18,the charger 41 is provided with an infrared control circuit 41 f and itstransmission/reception portion 41 g in correspondence with thetransmission/reception portion 34 b. The transmission/reception portion41 g is disposed at the mounting portion 41 b, for example. Incorrespondence with the transmission/reception portion 41 g, thetransmission/reception portion 34 b of the cassette 22 is disposed at aposition facing the transmission/reception portion 41 g when thecassette 22 is mounted in the mounting portion 41 b. The numeral 41 hdesignates a connection cord for connection to the external device. Inthe case that the cassette 22 is provided with a radio wavecommunication means or a wire communication means, the communicationmeans of the charger 41 should only be a type compatible with thecommunication means. Alternatively, the charger 41 may be provided withall types of communication means so that it can be compatible with avariety of cassettes.

With these configurations, communication can be carried out between thecharger 41 and the digital sensor cassette 22 while the secondarybattery 31 is charged. It is thus possible to communicate with theexternal device via the charger 41 when the charger 41 is connected tothe external device via the connection cord 41 h. Therefore, bytransferring a variety of data stored in the memory 22 f to the externaldevice, data processing, such as registration in database for use inimage reproduction and diagnosis after photographing, can be carried outby effectively using the time for charging.

By using the second battery 31 as a power supply as described above, nopower supply circuit is required for the main body of the panoramicradiographic apparatus. Therefore, the apparatus used with filmcassettes can easily be modified so that the apparatus can be used withdigital sensor cassettes. In addition, the trouble of preparing andconnecting a power cable is unnecessary.

Furthermore, the secondary battery 31 can be charged by mounting thecassette 22 in the charger 41, and communication to the external devicecan be carried out via the charger 41 during charging. Therefore, datacan be transferred to the external device by effectively using the timefor charging. For these reasons, data processing for reproduction ofimages, diagnosis after photographing and the like can be rationalized.

What is claimed is:
 1. A digital sensor cassette for a panoramicradiographic apparatus having a support for rotatably supporting arotary arm provided with an X-ray generator at one end of and an X-raydetector at the other end thereof, mounted in said X-ray detector,comprising at least one electric X-ray image detector disposed inface-to-face relationship with said X-ray generator via an X-ray shieldplate having a secondary slit and provided at said X-ray detector,driven based upon TDI control by control signals supplied from the mainbody of said panoramic radiographic apparatus in correspondence with therotation of said rotary arm, and used to convert X-rays to electricsignals to deliver image signals required for generating a panoramicX-ray image, electric X-ray signal detector being provided behind saidsecondary slit; an A/D converter for converting analog signals deliveredfrom said electric X-ray image detector into digital signals; aninput/output portion for communicating with an external circuit; and acontrol portion for electrically controlling the operations of saidelectric X-ray image detector, A/D converter and input/output portion;wherein said electric X-ray image detector comprises an image pick-updevice portion formed of a CDD sensor having two-dimensionally disposedpixels of an image pick-up device.
 2. A digital sensor cassette for saidpanoramic radiographic apparatus in accordance with claim 1, wherein theouter housing thereof is nearly identical with a film cassette loadedwith an X-ray film in shape, and said digital sensor cassette can bemounted in said cassette holder for said film cassette, provided in saidX-ray detector.
 3. A digital sensor cassette for said panoramicradiographic apparatus in accordance with claim 2, wherein said electricX-ray image detector comprises a light emitter for emitting light whenirradiated with X-rays, an optical fiber device for transmitting saidlight emitted from said light emitter, and an image pickup deviceportion for converting the light-emitting condition of said lightemitter transmitted by said optical fiber device into electric signals.4. A digital sensor cassette for said panoramic radiographic apparatusin accordance with claim 3, wherein said electric X-ray image detectoris housed in a case capable of shielding visible light, and the X-rayentry side of said case is formed of a material having hightransmittance for X-rays.
 5. A digital sensor cassette for saidpanoramic radiographic apparatus in accordance with claim 4, whereinsaid input/output portion is a wire type for making connections by usingconnectors and cables.
 6. A digital sensor cassette for said panoramicradiographic apparatus in accordance with claim 4, wherein saidinput/output portion is a wireless type for making connections viainfrared rays and radio waves.
 7. A digital sensor cassette for saidpanoramic radiographic apparatus in accordance with claim 5 or 6,wherein a secondary battery is used as a power supply for operation. 8.A digital sensor cassette for said panoramic radiographic apparatus inaccordance with claim 7, wherein, by mounting said cassette in a chargerprovided separately, said secondary battery can be charged, andcommunication to an external device can be carried out from saidinput/output portion via said charger during charging.